1. Field of the Invention
The present invention relates to techniques for coupling light from a point source, such as a single fiber, to an illumination fiber bundle, such as for an endoscope.
2. Description of the Background Art
Known techniques used for coupling light from a source cable to an illumination fiber bundle inside rigid or flexible endoscopes, for example, include (a) butt coupling or (b) coupling through a cone-shaped glass rod to focus the light before coupling it into the endoscope.
In either of the above cases, the fiber endfaces on both sides are epoxied and polished to the optical quality finish. The epoxy used typically has a 1-10% light absorption coefficient. The small percent of light which is absorbed by the epoxy combined with its poor heat transfer characteristics can gradually accumulate enough heat to melt the fiber endface. As a result, this prevents the use of a high power density light input to couple more light into the endoscope.